Miller Metal Co. makes a single product that sells for $43 per unit. Variable costs are $29.2 per unit, and fixed costs total $65,780 per month. Required: a. Calculate the number of units that must be sold each month for the firm to break-even. (Do not round intermediate calculations.) n volume units b. Assume current sales are $420,000. Calculate the margin of safety and the margin of safety ratio. (Round intermediate calculations to the nearest whole number.) Margin of safety Margin of safety ratio c. Calculate operating income if 6,400 units are sold in a month. (Do not round intermediate calculations.) d. Calculate operating income if the selling price is raised to $46 per unit, advertising expenditures are increased by $9,000 per month, and monthly unit sales volume becomes 7,100 units. (Do not round intermediate calculations.)